Foveon, Inc. (now Sigma Corporation) produces image sensors comprising an array of photosites, each of which includes three vertically-stacked photodiodes. Each of the three photosites responds to different wavelengths of light (i.e., each has a different spectral sensitivity curve). The Foveon technology is detailed, e.g., in U.S. Pat. Nos. 6,727,521, 6,731,397, 6,841,816, 6,958,862, 6,998,660, and 7,339,216.
Lytro, Pelican Imaging and others produce light field cameras that capture 4D light field information about a scene, through use of microlenses. Such “plenoptic imaging” systems are detailed, e.g., in patent publications 20070252074, 20080131019, 20080266655, 20100026852, 20100265385, 20110069189, 20110080487, and 20110122308.
Various companies have developed transparent semiconductors, transistors and electrodes useful in CMOS image sensors. Exemplary technology is detailed in Samsung's patent applications 20110156114 and 20090101948. Familiar transparent electrode materials include tin-doped indium oxide, zinc oxide, and carbon nanotube films. Additional information is provided in Ginsley, et al, Handbook of Transparent Conductors, Springer, 534 pp., 2011.
The artisan is presumed to be familiar with technologies involved in fabrication of semiconductor image sensors, including the foregoing.
In accordance with one aspect of the present technology, photosensors are again stacked. However, the stacking is considerably thicker than the prior art, making possible camera sensors that provide multi-focal length imaging, e.g., between six inches and infinity.
FIG. 1 introduces certain concepts used in the technology. Plural layers P1-P8 are stacked in an integrated structure, behind a lens system. Each layer comprises one or more photodetectors. The distance of each layer behind the lens corresponds to a different object distance, in accordance with the focal length of the lens. (I.e., the reciprocal of the object-lens distance, plus the reciprocal of the photodetector-lens distance, equals the reciprocal of the lens focal length.)
An image sensor can comprise a 2D array of such stacks, as illustrated schematically in FIG. 2.
The foregoing and many other features and advantages of the present technology will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings.